The federal officer killed while on duty near the Canadian border has been identified as a U.S. Air Force veteran who provided security at the Pentagon during the Sept. 11 attacks.

A police incident has closed Interstate 91 in Vermont, near the border with Canada, on Monday afternoon, state police said. The nature of the police incident, with Vermont State Police called “evolving” in a statement,

Agent David “Chris” Maland died in a shooting following a traffic stop, the FBI said. A second person killed in the incident was a German national in the country on a current visa, authorities said.